Is There A Term for Photographing People When They Aren t Aware of It Until After You ve Taken The Picture?

Poorly worded question, I know.
Basically, I m quite interested in just taking snaps of people in their natural state, not forcing them to behave a certain way or do something. Just a quick picture of them looking at the window thinking about something.
So, is there actually a professional term for this sort of... show more Poorly worded question, I know.
Basically, I m quite interested in just taking snaps of people in their natural state, not forcing them to behave a certain way or do something. Just a quick picture of them looking at the window thinking about something.

So, is there actually a professional term for this sort of photography?